This project continues to be a multidisciplinary approach to the investigation of various forms of experimental hypertension. The models of hypertension being studied are adrenal-regeneration hypertension, androgen-induced hypertension, DOC-induced hypertension and the spontaneously-hypertensive rat. The first two of these involve adrenal cortical dysfunction and the studies carried out include the analysis of the various enzyme systems involved in corticosteroidogenesis in the rat adrenal cortex. In addition, the circadian pattern of corticosteroids in blood is being determined using sensitive radioimmunoassays. These studies are being used to identify significant disturbances in adrenal cortical function which may result in excess mineralocorticoid secretion and, in turn, hypertension. Adrenal cortical function is also being investigated in the alterations in function as expressed in changes in mineralocorticoid/glucocortical ratios. The sensitivity of various strains of rat to DOC-induced hypertension is being re-examined with emphasis being placed on the resistant Wistar/Furth strain. A significant aspect of the studies involves correlating altered adrenal cortical function with the ultrastructure of the various zones of the adrenal cortex.